Puget Sound Energy is urging its 750,000 customers to lower their thermostats and limit hot water use at least through Wednesday.

The transmission pipeline, which is owned and operated by Enbridge, feeds Fortis B.C.'s system, among others.

Doug Stout of Fortis B.C. said Wednesday that 85 per cent of the gas his company feeds to homes and businesses is carried by the twinned pipeline that runs from northern British Columbia to the United States border south of Vancouver.

"Turn down your thermostat if you are in a cold spot. Turn off your furnace if you can, if you are in Vancouver or a situation where you can do that. Minimize the use of hot water if you have a natural gas hot water tank ... so we preserve the gas we have for as long as possible," said Stout.

As many as 700,000 customers in northern B.C., the Lower Mainland and Vancouver Island could be directly affected by a shortage, he said.

Stout urged another 300,000 customers in the Okanagan and southeastern B.C., to conserve even though their natural gas comes from Alberta.

"We are asking them to cut back, too, because we can flow some of that gas past them and down here to the Lower Mainland. So we are asking everybody to chip in," said Stout.

We are anticipating decreased energy flow and potential loss of service to some gas customers. We request that all gas customers across BC turn off their thermostats as well as reduce use of all other natural gas appliances. We appreciate your assistance: https://t.co/K0UslaGx7Y

The damaged Enbridge pipeline connects to the Northwest Pipeline system, which feeds Puget Sound Energy in Washington State and Northwest Natural Gas in Portland.

Puget Sound Energy is urging its 750,000 customers to lower their thermostats and limit hot water use at least through Wednesday.

Due to a pipeline rupture Tuesday in B.C., Canada, we’re asking you to help conserve natural gas and electricity tonight and Wednesday morning. Lowering your thermostat and limiting hot water use can help. Our local gas system is safe and was not damaged by the pipeline failure.

The rupture occurred on a natural gas transmission pipeline owned and operated by Enbridge about 13.5 kilometres from Prince George on Tuesday evening, Enbridge spokesman Michael Barnes said in an emailed statement.

It ignited at the site in Shelley, which is in a rural area. There are no reports of injuries, he said.

"Enbridge emergency crews have responded, have isolated and are currently depressurizing two natural gas transmission lines in the vicinity to contain the incident," he said. "The incident area has been cordoned off to maintain public safety."

Prince George RCMP said there were no reports of damage other than to the pipeline itself.

The cause of the rupture is under investigation, police said.

As of about 7:30 p.m. Tuesday — about two hours after the rupture was reported — the gas supply had been shut down.

About 100 people living on the north side of the Lheidli T’enneh reserve had to leave the area. Most have been allowed to return.

“I thought it might have been a jet engine or a low-flying jet,” Terry Teegee said of the noise. “And the next thing that came to mind is that maybe it’s a train, but that’s way too loud.

“But then, as soon as I looked outside, I saw a massive fireball about a half a kilometre to a kilometre away behind the community.”

He said the subsequent evacuation to the band’s community hall on the south side of the river was a “little bit frantic as you can imagine,” but everyone arrived safely.

Rodney Godwin and his family live on Estate Road, near the end of Landooz Road and just across the Fraser River from the Shelley townsite.

They heard what sounded like thunder just after 5:30 p.m. When Godwin looked across the way, he saw flames shooting into the sky.

The family left their home shortly after that.

The evacuation zone initially extended for several kilometres but was reduced to one kilometre, allowing some people to return home.

British Columbia’s Ministry of Environment said it has been notified that the incident involved 900 PSI gas line operated by Enbridge.

National Energy Board spokesman Tom Neufeld said the fire was along Enbridge's Westcoast main line, which falls under the board's jurisdiction.

The Westcoast Transmission System transports natural gas produced in the Western Canadian Sedimentary Basin to consumers in B.C. and, through interconnecting pipelines, other Canadian provinces and the United States.

"NEB inspectors have been deployed to this area. They're going to monitor and oversee the company's response to the incident, and they're going to determine the impact and extend of the fire and release," Neufeld said.

The NEB has also activated its emergency operations centre in Calgary, he said.

It will work closely with the Transportation Safety Board, which is responsible for investigating the incident, Neufeld said.